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This article in SSSAJ

  1. Vol. 39 No. 6, p. 1072-1076
    Received: Mar 3, 1975
    Accepted: July 28, 1975

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Soil Potassium Relationships as Indicated by Solution Equilibrations and Plant Uptake1

  1. D. A. Munn and
  2. E. O. McLean2



Four Ohio soils of wide range in K release capability were initially K-treated (0, 100, 200, 800 ppm) and successively cropped three times with corn in a growth chamber. Aliquots of the soils with and without K added and before and after cropping were assayed by extraction, equilibration, and plant uptake techniques for the effects of cropping and K-treatment. Uptake of K by the corn was closely related to the K release capabilities of the soils. Exchangeable K increased as rate of K increased. Initial cropping decreased the exchangeable K in all soils eliminating the effect of K treatments on exchangeable K. However, after initial cropping where no K was added, exchangeable K varied sixfold from the lowest to the highest. Nonexchangeable K removed with H2SO4 initially reflected K additions, but after the first crop, the values decreased progressively as K release capabilities of the soils increased. Parameters from Q/I isotherms of the soils gave correlations with percentage and total K contents of assay crops less satisfactory than for exchangeable and H2SO4 extractable K. There was a tendency for prior cropping to increase the fixation and reduce the plant recovery of subsequently applied K in the two soils high in clay and total K.

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